Technical Abstract:
The aim of this project is to increase the value of distillers grain by utilizing it as a feedstock for microwave assisted pyrolysis (MAP). Pyrolysis is the chemical/thermal conversion of biomass without the presence of oxygen into newly formed products: gases, liquids and solids. This conversion process is being investigated as a means of renewable energy production from biomass. The use of microwaves as the energy source for the pyrolysis reactions is emerging as one of the most attractive alternative technologies in the pyrolysis process. MAP overcomes some of the disadvantages to using biomass, mainly the water content and non-uniform heating rates. With traditional thermal pyrolysis the feedstock needs to be dried prior to the pyrolysis. This potential utilization of a wet feedstock by MAP significantly reduces processing time and required energy inputs. MAP has also been shown to positively influence the distribution of end-products to more liquid (bio-oil) products. The focus in this project is to evaluate the conversion of distillers grain by MAP into biochar and bio-oil. While producing direct energy products (syngas and bio-oil), we will also be producing a potential carbon sequestering and soil improvement agent (biochar). The percentage of biochar that can be produced through microwave assisted pyrolysis of distillers and corn stover mixtures does vary between 25 to 28% by weight. The yield of biochar was observed to be a function of the feedstock mixing ratio. Concurrently, the liquid phase yields also varied between 39 and 46% by weight, with the pure feedstock (distillers grain) yielding the maximum total liquid product. However, the quality of the produced bio-oil did vary as a function of the feedstock mixing ratio, with a 25% DDGS and 75% stover yielding the maximum hydrocarbon based liquid phase. The potential increase in soil fertility and carbon storage of these produced biochars is still under investigation and the results will be ready in time of the conference. The potential long-term outcomes are multifold. First, this research could lead to the development and promotion of additional bio-based energy production at ethanol plants by using MAP conversion of distillers grain. This increases the overall bioenergy production from the ethanol plant. Second, from this MAP process we would be producing a biochar that could be returned to the farmers’ fields, thus improving sustainable agricultural production. Producing the biochar at the ethanol plant would reduce the logistic hurdles of biomass delivery for pyrolysis and biochar delivery to agricultural fields, while providing additional potential economic products for the ethanol plant in biochar and the additional bioenergy.